The importance of selenium to human health is generally known. Based on the World Health Organization (WHO), an adult need about 50 µg Se per day. Unfortunately, most crops are poor with Se content that shed light on necessity of selenium enrichment of crops. Among vegetable crops, garlic and broccoli are considered as an excellent Se accumulator. Substitution of sulfuric amino acids by selenium amino acids (like: selenomethionine and selenocysteine) can disrupt biochemical reactions. High Se resistant plants can enter Se to non-protein amino acid compounds. Although the toxicity of Se in extra concentration for plants is clear, positive effects of low Se concentration on plant protection against abiotic stress, reactive oxygen species and activation of oxidative stress ameliorating systems have been reported. In human, the line between Se deficiency and toxicity is thin related to chemical form of Se. As a result of Se toxicity risk for human, before any crop enrichment plan, the average Se intake by individuals and Se content of soil must be carefully premeditated in different regions of the country.